Age-group differences in speech identification despite matched audiometrically normal hearing: contributions from auditory temporal processing and cognition.

Christian Füllgrabe,Brian C J Moore,Michael A Stone

doi:10.3389/fnagi.2014.00347

Abstract

Hearing loss with increasing age adversely affects the ability to understand speech, an effect that results partly from reduced audibility. The aims of this study were to establish whether aging reduces speech intelligibility for listeners with normal audiograms, and, if so, to assess the relative contributions of auditory temporal and cognitive processing. Twenty-one older normal-hearing (ONH; 60–79 years) participants with bilateral audiometric thresholds ≤ 20 dB HL at 0.125–6 kHz were matched to nine young (YNH; 18–27 years) participants in terms of mean audiograms, years of education, and performance IQ. Measures included: (1) identification of consonants in quiet and in noise that was unmodulated or modulated at 5 or 80 Hz; (2) identification of sentences in quiet and in co-located or spatially separated two-talker babble; (3) detection of modulation of the temporal envelope (TE) at frequencies 5–180 Hz; (4) monaural and binaural sensitivity to temporal fine structure (TFS); (5) various cognitive tests. Speech identification was worse for ONH than YNH participants in all types of background. This deficit was not reflected in self-ratings of hearing ability. Modulation masking release (the improvement in speech identification obtained by amplitude modulating a noise background) and spatial masking release (the benefit obtained from spatially separating masker and target speech) were not affected by age. Sensitivity to TE and TFS was lower for ONH than YNH participants, and was correlated positively with speech-in-noise (SiN) identification. Many cognitive abilities were lower for ONH than YNH participants, and generally were correlated positively with SiN identification scores. The best predictors of the intelligibility of SiN were composite measures of cognition and TFS sensitivity. These results suggest that declines in speech perception in older persons are partly caused by cognitive and perceptual changes separate from age-related changes in audiometric sensitivity.

Highlights

IntroductionAging in adults is associated with deterioration and increased effortfulness of all levels of speech processing (from identification to comprehension), especially in noisy and reverberant conditions (e.g., CHABA, 1988)
Aging in adults is associated with deterioration and increased effortfulness of all levels of speech processing, especially in noisy and reverberant conditions (e.g., CHABA, 1988)
The results presented will mainly be compared to those for studies using fairly stringent definitions of normal audiograms and using lowpass-filtered target speech to restrict the spectrum of the stimuli to the frequency range where audiometric thresholds were normal, or to studies where age groups were audiometrically matched

Summary

Introduction

Aging in adults is associated with deterioration and increased effortfulness of all levels of speech processing (from identification to comprehension), especially in noisy and reverberant conditions (e.g., CHABA, 1988). It has become apparent that hearing-impaired people report a lower quality of life (Dalton et al, 2003), experience more social isolation (Weinstein and Ventry, 1982; Strawbridge et al, 2000) and depression (Gopinath et al, 2009; Huang et al, 2010), and show poorer cognitive functioning and accelerated cognitive decline (Lin et al, 2011, 2013) than normal-hearing people This suggests that speech communication difficulties constitute a socio-psychological handicap for the affected person (Arlinger, 2003) and represent an important financial burden for society in terms of social and health care provision (Mohr et al, 2000; Hjalte et al, 2012; Foley et al, 2014). One possible explanation for this is that age-related changes in supra-threshold auditory processing and cognition— that are not captured by an audiometric assessment—contribute to the speech-identification difficulties of older people (e.g., Humes et al, 2013b; Moore et al, 2014; Schoof and Rosen, 2014)

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